1. Field of the Invention
The present invention relates to a display device and a method for fabricating the same, and more particularly, to an LCD device for switching a display mode between a wide viewing angle and a narrow viewing angle and a method for fabricating the same.
2. Description of the Background Art
In general, a liquid crystal display (LCD) device is used as a flat panel display device because of its high picture quality and a low consumption power. The LCD device is constructed to control an optical transmittance of a liquid crystal between two substrates by controlling the intensity of an electric field applied across the liquid crystal layer. The LCD device is being widely used in notebook computers, personal digital assistants (PDAs), video telephones, televisions and various other portable electronic devices.
In response to user's demand, LCD devices are being developed that have a large screen, fine pitch, and a wide viewing angle. There are two types of related art LCD devices having a wide viewing angle. The first is an LCD device driven by a horizontal field driving method and the second is an LCD device using a compensated film with a vertical alignment (VA) method.
In the LCD device driven by a horizontal field driving method, a pixel electrode and a common electrode are formed on the same substrate. An electric field horizontal to the substrate is formed between the pixel electrode and the common electrode when the pixel electrode is turned on. Accordingly, a long axis of the liquid crystal molecules is operated in parallel with the substrate corresponding to the on/off state of the pixel electrode. As a result, a refractive index of the liquid crystal observed by the user's naked eyes remains small so that there in an excellent contrast ratio and a wide viewing angle.
In the LCD device using a compensated film with a vertical alignment (VA) method, a wide viewing angle is implemented by attaching a compensation film at an inner side of a polarizing plate. More particularly, the LCD device using a compensated film with a vertical alignment (VA) method includes a pair of transparent substrates each having a transparent electrode at an inner surface thereof. Polarizing plates, which are perpendicular to each other, are at outer surfaces of the pair of transparent substrates. The compensation film is between one of the transparent substrates and one of the polarizing plates. A liquid crystal material between the two substrates is aligned to be perpendicular to the substrate by rubbing at least one of the electrodes. Recently, a mode in which the liquid crystal molecules are divided into groups by forming an opening pattern or a protrusion on a transparent electrode without performing a rubbing has been proposed. A typical LCD device for implementing a viewing angle will be explained with reference to FIG. 1.
FIG. 1 is a cross-sectional view of a liquid crystal display (LCD) device in accordance with the related art. As shown in FIG. 1, the related art LCD device includes a thin film transistor (TFT) array substrate 11 and a color filter substrate 41 facing and attached to the TFT array substrate 11 with a cell gap therebetween. A liquid crystal layer 51 is formed in the cell gap between the TFT array substrate 11 and the color filter substrate 41.
On the TFT array substrate 11, pixels are arranged in a matrix form. A thin film transistor 20, a pixel electrode 27, and a capacitor (not shown) are formed in each pixel. The thin film transistor 20 includes a gate electrode 13 formed on the TFT array substrate 11, a gate insulating layer 15 formed on the gate electrode 13, a semiconductor layer 17 formed on the gate insulating layer 15, and source/drain electrodes 21 and 23 formed on the semiconductor layer 17 and spaced from each other. A passivation layer 25 is formed across a surface of the TFT array substrate 11, including the source/drain electrodes 21 and 23. A pixel electrode 27 is electrically connected to the drain electrode 23 through a drain contact hole (not shown) formed in a passivation layer 25.
Red, Green, and Blue color filters 45 in a black matrix 43 are formed on the color filter substrate 41 for implementing colors in the LCD device. A common electrode 47 is formed on the color filter substrate 41 for applying an electric field to the liquid crystal layer 51. An alignment layer (not shown) is formed at an inner surface of the TFT array substrate 11 and at an inner surface of the color filter substrate 41. The liquid crystal 51 is oriented (not shown) in a predetermined direction by rubbing the alignment layer (not shown).
The color filter substrate 41 and the TFT array substrate 11 are respectively provided with a first polarizing plate 61 and a second polarizing plate 63. The polarizing plates 61 and 63 polarize natural light having vibrations in several directions into one direction. The liquid crystal is rotated by a dielectric anisotropy when an electric field is applied between the pixel electrode 27 formed at each pixel of the TFT array substrate 11 and the common electrode 47 formed at the inner surface of the color filter substrate 41. Accordingly, images are displayed by passing the polarized light through specified pixels and/or by preventing the polarized light from passing through specified pixels.
In the LCD device, light 71 from a backlight is emitted to a back surface of an LCD panel through several diffusion sheets (not shown) in order to obtain a uniform brightness. As the light passes through to the front surface of the LCD panel, an image can be displayed with a wide viewing angle by using a compensation film between the color filter substrate 41 and the polarizing plate 61. Otherwise, the related art LCD device in FIG. 1 will have a narrow viewing angle.
The related art LCD device has the following problems. A wide viewing angle can not be actively controlled so as to have a narrower viewing angle. Although not shown, a viewing angle can be narrowed by applying a film-type filter or an optical fiber to the LCD panel. Typically, a narrower viewing angle is brighter than a wide viewing angle. However, a display mode in the related art can not be switched between a wide viewing angle and a narrow viewing angle.